Liquid-cooled burner for open hearth furnaces



Jan. 11, 1966 GRAHAM ETAL LIQUID-COOLED BURNER FOR OPEN HEARTH FURNACES2 Sheets-Sheet 1 Filed NOV. 20, 1963 mwm M ww F N 1 i, a

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LIQUID-COOLED BURNER FOR OPEN HEARTH FURNACES Filed NOV. 20, 1963 2Sheets-Sheet 2 M9 lzliiilm R.

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\ INVENTORS Hugh 51 Graham BY W/'///'am M. C/l'ne Richard J Rambo/cUnited States Patent 3,228,612 LIQUID-(300L131) BURNER FOR OPEN HEARTHFURNACES Hugh S. Graham, Bethlehem, William M. Cline, Coopershurg, andRichard J. Reinhold, Bethlehem, Pa., assignors, by mesne assignments, toBethlehem Steel Corporation, a corporation of Delaware Filed Nov. 20,1963, Ser. No. 325,033 4 Claims. (Cl. 239132.3)

This invention relates in general to combination burners for introducingliquid and/or gaseous fuels into a high temperature furnace, and inparticular to that type of burner which is provided with a liquidcoolant.

In a regenerative reversing type open hearth furnace, it is usual tohave one burner in each end wall of the furnace. Eflicient operation ofthe furnace requires the incoming air necessary for combustion to beheated before it enters the hearth. This heating is accomplished bypassing the air over a heated brickwork called regenerators. Theregenerators are heated by the hot waste gases of combustion. The normaloperation of these furnaces therefore requires a periodical reversal ofthe path of the hot waste gases. The burners are operated intermittently-the burner in one wall is shut off and the burner in the oppositewall is ignited. The flame of the operating burner passes over theliquid bath toward the opposite end wall. The hot waste gases ofcombustion are directed to the opposite end wall, pass over theinoperative burner positioned in the end wall, to the downtakes, throughthe regenerators which are heated by the gases and out the furnacestack. Air for the operating burner comes into the furnace through thehot regenerators located on the same side of the furnace, where it isheated by the brickwork. When the regenerators are no longer able tosufliciently heat the incoming air of combustion, the operation of thefurnace is reversed, that is, the inoperative burner is ignited and theoperating burner is turned ofi. This intermittent operation results inthe upper surfaces of the burner being exposed to the high temperaturesof the hot waste gases during the inoperative period and the lowersurfaces of the burner being exposed to the high temperatures of thefurnace and incoming air during operating periods. It is thereforeessential to protect the exposed surfaces of the burners from the hightemperatures prevailing in the furnaces.

Substantially all of the prior art burners are of the liquid-coolanttype which use water under relatively low pressure and at lowtemperature as the coolant. Generally two types of burner constructionhave been used. One type of construction consists of concentricallyarranged fuel tubes surrounded by an outer casing or water jacket. Thesecond type of construction consists of fuel tubes arranged insubstantially parallel relationship to each other inside an outer casingor water jacket. Liquid fuel is supplied in the lower tube and gaseous,semi-liquid or liquid fuels are supplied in the upper tube. In bothtypes the water coolant is introduced into the water jacket at thenozzle end of the burner either by a tube which is encased in the waterjacket itself or by a tube on the outside of the water jacket which issubstantially parallel to the outer casing and is connected thereto by apassageway at the nozzle end. These arrangements allow the coolant toflow around the nozzle thence rearwardly through the water jacket to acoolant outlet.

All of the above prior art burners are susceptible to stagnation orentrapment of water in a dead space near the front end of the burner inthe area exposed to the high temperature of the furnace. This conditionresults from the lack of positive pressure uniformly distributed acrossthe entire area of the stream of cooling water.

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Steam is thus formed by the heating of the stagnant or entrapped waterresulting in a loss of the heat transfer capability of the water causinglocalized overheating resulting in early burnout of the burner. Also,because of the low inlet pressure any sediment brought into the burnerwith the water is deposited and accumulates in the burner.

It is the primary object of this invention to provide a burnerconstruction of the evaporative-cooler type in which the cooling is soeffective that a greater portion of the burner can be exposed to thehigh temperatures encountered in an open hearth furnace.

It is a further object of this invention to provide a burner of theevaporative-cooler type which can be used in a high temperature furnaceand which is so constructed that the water coolant can be used at higherpressures and higher temperatures than heretofore have been used.

It is also an object of this invention to provide a bumer of theevaporative-cooler type which has no impediments to the flow of coolantthrough the water passages thus removing the possibility of waterstagnating or being entrapped with its resultant steam formation, lossof heat transfer capabilities and early burnout.

It is a further object to provide means to accommodate the differentialexpansion and contraction of the various parts of our burner.

Our burner broadly comprises a pair of spaced substantially parallelfuel tubes each having a rear end and a forward end. Each fuel tube issurrounded by an outer casing or liquid cooling jacket extending fromthe rear end to the forward end of the fuel tube. One of the outercasings has a liquid coolant inlet at its rear end. The other outercasing has a liquid coolant outlet at its rear end. The liquid coolantjackets are connected at their forward or nozzle ends by a shortpassageway. The cross-sectional area of each of the pairs of tubes issubstantially constant the entire length of the burner. The coolant isintroduced into the inlet at the rear of one outer casing, flowsforwardly to the connecting passageway at the forward end of the outercasings, through the said passageway to the other outer casing andrearwardly to the outlet pipe in the rear of the said other outingcasing.

No internal structures are required to keep the pipes apart. Therefore,there is nothing to impede the flow of water through the coolantpassages. This aids in avoiding the possibility of water collecting in adead spot where the heat of the furnace can turn it into steam thusreducing the rate of heat transfer and causing localized overheating andburnout of the burner.

FIG. 1 shows a longitudinal sectional view of the burn er assembly;

FIG. 2 is an exploded view of the packing gland at the rear of theburner;

FIG. 3 is a cross-sectional view of the burner assembly taken throughline 3-3 of FIG. 1;

FIG. 4 is another embodiment of the invention showing a removable tubeinserted into the gaseous fuel line to burn pitch or pitch-like fuels.

FIG. 5 shows the burner encased in a castable refractory.

Referring now to the drawings of the invention, we shall describe ourinvention in more specific detail. A longitudinal sectional view of theburner assembly is shown in FIG. 1. The burner assembly is made up oftwo pairs of substantially concentrically arranged tubes, one pair oftubes 1 being placed above the other pair of tubes 2 in a substantiallyparallel relationship and being spaced therefrom by a spacer assembly 3.Each burner has an outer coolant casing surrounding an inner fuel tube.Only liquid fuel is supplied to the nozzle of the .prevents overheatingof the outer casing.

burner through the lower fuel tube. The upper fuel tube may be used tosupply gaseous fuel, liquid fuel or semiliquid fuel to the nozzle of theburner. The cross-sectional area of each pair of tubes is substantiallyconstant the entire length of the burner. The outer casing4 of the lowerpair of tubes which surrounds the inner fuel tube 5 is connected to theouter casing 6 of the upper pair of tubes which surrounds the inner fueltube 7, by means of the connecting passage 8. The outer casing 4 isprovided with a water inlet 9 near its rear portion. The outer casing 6is provided with a water outlet 10.near its rear portion. The rearportion of the fuel pipe 7 is connected to a Y-shaped coupling .11. Afuel line fiange 12 is fixed to the end of one leg of the Y-coupling 11so that a gaseous fuel line (not shown) may be attached thereto. A fueltube coupling coupling 13 is threaded onto the other leg of theY-coupling '11 for easy attachment of a liquid fuel line (notshown).

The outer casing 6 is made larger in cross sectional area than outercasing 4, to accommodate the larger fuel pipe 7 The larger fuel tube 7is necessary to accommodate the volume of gaseous fuel necessaryto meetthe ti.- .ing requirements of the furnace. In times of gaseous fuelshortagee.g. coke oven gas in short supply-a fuel pipe 14 may beinserted into the fuel pipe 7, concentrically aligned therewith, toprovide a passage for a pitch or tarlike fuel as shown in FIG. 4. Thefuel tube coupling 13 makes it possible .to couple the liquid fuel line(not shown), without removing the burner from the furnace. In this waythe gaseous fuel tube does not become clogged with the residue usuallyassociated with semi-solid fuel and it is only necessary to remove fueltube 14 to again burn coke oven gas when in plentiful supply.

Although the cross-sectional areas of outer casing 6 and fuel tube -7are larger than the cross-sectional areas of outer casing 4 and fueltube 5, the space 15 available for passage of water between tubes 6 and-7 is smaller than the space 16 available for passage of water betweentubes .4 and 5. Therefore to remove the amount of water being introducedinto the burner at inlet 9, there must be an increase in velocity of thewater flowing in passage 15 over the velocity of the Water in passage 16Thevelocity of the water in both burner tubes is sufficient to preventany stagnation or Stratification of water flow which might result inlocalized overheating and steam formation, decreasing the heat transfercapabilities of the coolant and resulting in early failure of the burnerdue to a burnout.

To cool the burner in operation in the furnace, water is supplied underpressure into the outer casing 4 through the inlet port 9. The waterflows forwardly through passage 16 to the nozzle end of the burner,through the connecting passage 8 to the outer casing 6, makes a 180 turnand flows backwardly through passage 15. at a higher velocity to thewater outlet port 10, thence to an expansion tank (not shown). In theexpansion :tank, a portion of .the circulating water flashes intosteamand leaves the system. The remaining water is recirculated to again coolthe burner. In this manner the heat from the burner walls is removed aslatent heat and the circulating water is maintained at its saturationtemperature for its particular flowing pressure. As a result there is noexcessive rise in the water temperature in the burner and the watervelocity The water velocity, or flow rate, is thereby sufiicient toprevent the formation of steam in the burner with a resultant localizedoverheating and early burnout of the burner cooler.

The burner which may be approximately fourteen (14) feet in length, isinserted into the furnace at about a 7 angle to the furnace hearth andextends into the furnace for approximately eight feet. The portion ofthe burner which extends into the furnace is exposed to the highesttemperatures, being directly within the heat affected zone. Therefore,we may further protect this section of the burner from the high furnaceheat by encasing the middle portion of the burner in a castablerefractory material 17 as shown in FIG. 5. In addition, the castablerefractory on the burners reduces the amount of heat transferred fromthe furnace to the burner. Although this heat quantity is small comparedto the total heat quantities in the furnace, it is nevertheless the hightemperature lev'el heat that is important in steel making.

As noted above, approximately eight feet of the burner will be in aheat-affected zone in the furnace. The .heataffected area of the burnerwill expand to a greater degree than will the cooler rear portion of theburner. Also, the hotter outer casing will expand to a greater degreethan will the inner fuel tube which is more fully protected by thecooling water. The uneven expansion of the front and back areas of theouter casings and the uneven expansion of the outer casings and theinterior fuel tubes set up stresses in the metallic fuel tubes and outercasings which may be of suflicient strength to break the-welds and pullthe tubes apart. For this reason, each pair of tubes is equipped with apacking gland expansion joint at the rear of the burner. Since bothpairs of tubes have the same type of packing gland expansion joint andeach of the tubes is subjected to the same type of uneven expansion onlythe upper packing gland expansion joint, FIG. 2, will be described.

The gland body 18 of the expansion joint is welded to the outer casing6. A suitable O-type sealing ring 19 made of a suitable material such ascotton impregnated with graphite, neoprene, or other rubber-likeresilient material is inserted into the body of the gland so that itseats on the shoulder 20. A cylindrical ferrule 21 is then inserted intothe gland, said ferrule abutting the sealing ring 19. The backing ring22 seats on the ferrule 21 and when the nut 23 is drawn up on the bolt24, the backing ring 22 bears against the ferrule 21 which in turncompresses the sealing ring 19. The sealing ring 19 is forced inwardly.to form a tight seal around the fuel tube 7 thus preventing leakage ofwater toward the rear of the burner. The fuel tube 7 can move freelywithin the sealing ring 19 thus allowing the said fuel tube 7 tocontract or expand independently of the outer casing 6. It is alsopossible for the outer casing6 to contract or expand independently ofthe fuel tube 7. The independent movement .of the outer casing 6 andfuel tube 7 prevents the formation of stresses in the tubes thuspreventing the failure of any welds in the burner.

The pairs of tubes of the burner assembly are spaced apart and kept insubstantially parallel relationship by the spacer assembly shown inFIGS. 1 and 3. Referring to FIG. 3, the cooler saddles 25 are welded tothe outer casing 6. Pins 26, extending through the cooler saddles arewelded to the outer casing 6. Cooler saddles 27 are welded to the outercasing 4. Spacer or side plates 29 are bolted to the cooler saddles 27by means of .bolts 28. Pins 26 extend through elongated slots 30 of thespacer plates 29.

During the period of time when a burner is inopera tive, the uppersurfaces of the burner are subjected to the heat of the waste gases intheir movement to the re- :generators. These upper surfaces, beinghotter than the lower surfaces of the burner, will expand to a greaterextent than will the protected lower surfaces. On the other hand, whenthe burner is operating, the lower surfaces are exposed to the heat ofthe incoming air and will expand more than the upper surfaces of theburner which are somewhat protected from the hot incoming air. Both ofthese conditions of uneven expansion of the pairs of tubes, if suchtubes were rigidly connected, could result in the buckling of one pairof tubes or in the tearing of .the welds at the nozzle end of theburner. It is therefore important that the parallel pairs of concentrictubes be capable of expanding or contracting independenly of eachother.. This is accomplished by providing the slots. 36 in the spacerassembly shown in FIGS. 1 and 3. During the inoperative period, theupper pair of tubes, fuel tube 7 and outer casing 6 will tend to ex pandmore than the lower pair of tubes, fuel tube 5 and outer casing 4. Theexpansion must be in a rearward direction since outer casings 6 and 4are attached to each other by welding coolant passage 8 thereto, andouter casings 6 and 4 are attached to the fuel tubes 7 and 5,respectively, by Welds at the said fuel tube-s outlet ends. The pins 26welded to outer casing 6 will slide in the slot 30 thus allowing therearward expansion of the said pair of tubes to occur without any damageto the burner. Conversely during the operative period outer casing 4 andfuel tube 5 will be exposed to the hot temperatures of the incoming airand will expand more than the outer casing 6 and fuel tube 7. The spacerassembly being Welded to outer casing 4 Will move with the expansion ofthis said outer casing 4. The slot 30 in spacer plate 29 will allow thisrearward movement to occur without damage to the burner.

In a specific example of the use of our burner, we constructed a burnerwhich had an overall length of 13 feet 4 inches. The lower pair ofconcentrically aligned tubes comprised a fuel tube made of schedule 40steel pipe having an inside diameter of 1.6 inches and an outsidediameter of 1.9 inches and a coolant jacket made of schedule 80 steelpipe having an inside diameter of 3.36 inches and an outside diameter of4.0 inches. The upper pair of concentrically aligned tubes comprised afuel tube made of schedule 40 steel pipe having an inside diameter of2.5 inches and an outside diameter of 2.875 inches and a coolant jacketmade of schedule 80 steel pipe having an inside diameter of 3.826 inchesand an outside diameter of 4.50 inches. The burner Was inserted into anopen hearth furnace for a distance of 8 feet.

Water at the rate of 155 gallons per minute under a pressure of 42pounds per square inch gauge and at a temperature of 245 F. was suppliedto the inlet port 9 of the burner. The outlet water temperature wasfound to be 260 F. and had a pressure of 27 pounds per square inch. Thevelocity of the water flowing forwardly in the lower water jacket was8.2 feet per second. This increased to a velocity of 10.0 feet persecond in the upper water jacket.

After the burner had been in continuous operation for one month(approximately 90 heats of steel were processed) it was removed from thefurnace and the tubes were examined by cutting them in half in alengthwise direction. No evidence of accumulated sediment nor anyevidence of corrosion or erosion due to entrapped water and subsequentsteam formation was noted.

In another furnace campaign with a burner cooler of the same design, thepressure in the closed system was raised so that the cooling conditionschanged. Water at the rate of 135 gallons per minute under a pressure of200 pounds per square inch gauge and at a temperature of 360 F. wassupplied to the inlet port of the burner. The outlet water temperaturewas found to be 370 F. at a pressure of 160 pounds per square inchgauge.

With operation of the burner cooler at the aforementioned pressures andseveral intermediate pressures the burner performed Well, thusindicating a wide flexible range of cooling ability.

Although we have described our invention as a combination gas and oilburner particularly adapted to be used in an open hearth furnace, itwill be understood that it can be used with other types of furnaces andthat we can use any desirable combination of fuels and we can use liquidfuel or gaseous fuel alone. We do not wish to be limited to the exactand specific details shown and described but can use such substitutions,modifications or equivalents thereof as are embraced within the scope ofour invention.

. We claim:

1. A liquid-cooled burner for use in high temperature furnaces, having astructure comprising:

(a) a pair of spaced substantially parallel fuel pipes each having arear end and a forward end,

(b) a liquid-coolant jacket surrounding one of said fuel pipes andspaced uniformly therefrom to form a coolant passage and extending fromthe rear end to the forward end thereof,

(0) a liquid-coolant jacket surrounding the other of said fuel pipes andspaced uniformly therefrom to form a coolant passage and extending fromthe rear end to the forward end thereof,

(d) a water inlet at the rear end of one of the said liquid-coolantjackets,

(e) a water outlet at the rear end of the other of said liquid-coolantjackets,

(f) a liquid-coolant passage connecting the forward ends of said waterjackets,

(g) packing glands comprising a packing gland body secured to each ofthe said liquid-coolant jackets, a sealing ring inserted therein tocommunicate with the shoulder thereof, a ferrule abutting said sealingring, a backing ring seating on said ferrule, said backing ring bearingagainst said ferrule to encompass the said sealing ring to preventleakage of water rearwardly through the packing gland but allowing freemovement of said fuel pipes encircled by said sealing ring,

(h) means to permit one liquid-coolant jacket to move relative to theother liquid-coolant jacket.

2. A liquid-cooled burner for use in a high temperature furnace asclaimed in claim 1 in which the said means of subparagraph (h) forrendering one liquid-coolant jacket slidably movable relative to theother liquid-coolant jacket, is a spacer assembly, said spacer assemblycomprising a pair of cooler saddles secured to the liquidcoolant jacketof one of the fuel pipes, a pair of spacer plates secured to the saidpair of cooler saddles, a pair of cooler saddles secured to theliquid-coolant jacket of the other fuel pipe, a pair of pins secured tothe liquidcoolant jacket of the said other fuel pipe, said pinsextending radially outwardly from the surface thereof through a pair ofslots in the said spacer plates, said pins being freely movablelongitudinally in said slots in said spacer plates.

3. A liquid-cooled burner for use in high temperature furnaces, having astructure comprising:

(a) a pair of spaced substantially parallel fuel pipes each having arear end and a forward end,

(b) a liquid-coolant jacket surrounding one of said fuel pipes andspaced uniformly therefrom to form a coolant passage and extending fromthe rear end to the forward end thereof,

(c) a liquid-coolant jacket surrounding the other of said fuel pipes andspaced uniformly therefrom to form a coolant passage and extending fromthe rear end to the forward end thereof,

(d) a water inlet at the rear end of one of the said liquid coolantjackets,

(e) a water outlet at the rear end of the other of said liquid-coolantjackets, and

(f) a liquid-coolant passage connecting the forward ends of said waterjackets,

(g) means to permit the fuel pipes to move relative to theliquid-coolant jackets surrounding the said fuel P P (h) said meanscomprising a pair of cooler saddles secured to the liquid-coolant jacketof one of the said fuel pipes, a pair of spacer plates secured to thesaid pair of cooler saddles, a pair of cooler saddles secured to theliquid-coolant jacket of the other fuel pipe, a pair of pins secured tothe liquid-coolant jacket of the said other fuel pipe extending radiallyoutwardly from the surface thereof, through a pair of slots in the saidspacer plates, said pins being 8 freely movable longitudinally in saidslot s in. said ('g) means in substantially spaced relationship to saidspacerplates. 7 v forward-ends securing said jackets to each other in 4.A liquid-cooled burner for use in a high temperature movablere1ationship furnace, comprising:

( pg p g i y pa g -P p ReferencesCited by the Examiner eac avlngarear enan a orwar en (b) separate liquid coolant jackets surrounding eachUNITED STATES PATENTS of said fuel pipes'and extending from the rear end1,707,772 4/1929 Robinson.

to the forward end thereof, 2,338,686 1/1944 Gredell 28534l X (c) eachof said jackets being fixedly secured to the 10 forward end of itsrespective fuel'pipe and being FOREIGN PATENTS movably secured to therear end of its respective fuel 9,209 1894 Great Britain. pipe by apacking gland, 94,000 4/ 1922 Switzerland. (d) a liquid coolant inlet atthe rear end of one, of

said jackets, 15 FREDERICK L. MATTESON, JR., Primary Examiner.

(e) a liquid coolant outlet at the rear end of the other MEYER PERLIN,JAMES WESTHAVER,

of sa1d ackets, Examiners (f) a liquid coolant passage connecting theforward ends of said jackets, and

1. A LIQUID-COOLED BURNER FOR USE IN HIGH TEMPERATURE FURNACES, HAVNG ASTRUCTURE COMPRISING: (A) A PAIR OF SPACED SUBSTANTIALLY PARALLEL FUELPIPES EACH HAVING A REAR END AND A FORWARD END, (B) A LIQUID-COOLANTJACKET SURROUNDING ONE OF SAID FUEL PIPES AND SPACED UNIFORMLY THEREFROMTO FORM A COOLANT PASSAGE END EXTENDING FROM THE REAR END TO THE FORWARDEND THEREOF, (C) A LIQUID-COOLANT JACKET SURROUNDING THE OTHER OF SAIDFUEL PIPES AND SPACED UNIFORMLY THEREFROM TO FORM A COOLANT PASSAGE ANDEXTENDING FROM THE REAR END TO THE FORWARD END THEREOF, (D) A WATERINLET AT THE REAR END OF ONE OF THE SAID LIQUID-COOLANT JACKETS, (E) AWATER OUTLET AT THE REAR END OF THE OTHER OF SAID LIQUID-COOLANTJACKETS, (F) A LIQUID-COOLANT PASSAGE CONNECTING THE FORWARD ENDS OFSAID WATER JACKETS, (G) PACKING GLANDS COMPRISING A PACKING GLAND BODYSECURED TO EACH OF THE SAID LIQUID-COOLANT JACKETS, A SEALING RINGINSERTED THEREIN TO COMMUNICATE WITH THE SHOULDER THEREOF, A FERRULEABUTTING SAID SEALING RING, A BACKING RING SEATING ON SAID FERRULE TOENCOMPASS ING RING BEARING AGAINST SAID FERRULE TO ENCOMPASS THE SAIDSEALING RING TO PREVENT LEAKAGE OF WATER REARWARDLY THROUGH THE PACKINGGLAND BUT ALLOWING FREE MOVEMENT OF SAID FUEL PIPES ENCIRCLED BY SAIDSEALING RING, (H) MEANS TO PERMIT ONE LIQUID-COOLANT JACKET TO MOVERELATIVE TO THE OTHER LIQUID-COOLANT JACKET.